1. Field of the Invention
The present invention relates to an aberration estimating method for measuring an aberration of a test optical system, a program, and an image-pickup apparatus.
2. Description of the Related Art
Several methods have conventionally been suggested each of which measures an aberration of a test optical system without a measuring device such as an interferometer and a shack-hartmann sensor. For example, D. Russell Luke, James V. Burke, Richard G. Lyon, Optical Wavefront Reconstruction: Theory and Numerical Methods, Usa, Siam Review, Society of Industrial and Applied Mathematics, 2002, Vol. 44, p. 169-224 (“Luke et al.”) suggests an optimization method for estimating an aberration of a test optical system from a plurality of images acquired by changing a focus when a light source is a point light source (such as a star). R. Miyakawa, P. Naulleau, A. Zakhor, K. Goldberg, Iterative Procedure for In-situ Optical Testing with an Incoherent Source, Proceedings of Spie, (USA) Spie Press, 2010, Vol. 7636, p. 76361k-1˜76361k-7 (“Miyakawa et al.”) suggests a method of illuminating an object by an extensive light source, that is, a partially coherent illumination, and of estimating an aberration using the genetic simulated annealing from a plurality of images acquired by changing a focus. However, the genetic simulated annealing requires a long time for calculations. The steepest descent method configured to search for a minimum value of a function from a slope of the function (first derivative) is known as a relatively fast optimization method. Japanese Patent Laid-Open No. (“JP”) 2007-163461 suggests a method for estimating an aberration of a test optical system by illuminating an object by a partially coherent illumination, and using the steepest descent method based on positional shifts of a plurality of images acquired by changing a focus. However, the estimation accuracy decreases when an aberration is estimated only from the positional shift.
Each of the above prior art references requires a long time for calculations, and it is difficult to quickly and precisely measure an aberration of a test optical system.